A gas insulated switchgear (hereinafter, abbreviated as “GIS”) is a switch with which load current of an electric power system or an electric power apparatus is opened and closed, and further accident current or the like is broken to protect the equipment in the load side and to prevent the accident spread in the upstream side. Accordingly, the GIS is an important infrastructure apparatus that supports the stable supply of electric power. In a tank of a GIS, a lubricant such as grease and wax is used for the sliding parts of electrodes, and a mechanism part for operating the electrodes. The lubricant is used to reduce frictional resistance and abrasion in each of the sliding parts, and required for reliable operation at the time of current breaking.
As a technique of a lubricant to be used for a gas insulated switchgear, for example, there is PTL 1 (JP 50-30645 B). In PTL 1, there is a disclosure of a conductive lubricant that is characterized by including: (a) a mineral oil-based lubricant in a base oil; (b) a high-melting point wax in a thickener; (c) at least one kind selected from powder of an intermetallic compound constituted of at least one kind of element among groups 5 and 6 of the periodic table as the essential component, and graphite powder, in a conductivity imparting agent; and (d) 0.5 to 6% by weight of at least one kind of low polymers of a chloroethylene derivative represented by a predetermined formula in a lubricity improver. A turbine oil as a mineral oil, a high-melting point wax (amide wax, or the like) as a thickener, graphite and NbS2 as a conductivity imparting agent, polyvinyl chloride as a lubricity improver, and the like have been disclosed in PTL 1. The conductive lubricant in PTL 1 is for the purpose of being used in a disconnector of a GIS, and deterioration during the storage period and decrease of the lubrication performance during the long-term use, which were problems of a lubricant in which graphite was dispersed in a mineral oil at that time, have been solved by lubricating waxing.
Further, in PTL 2 (JP 2001-101943 A), there is a disclosure of a power circuit switch comprising: an operating mechanism including a plurality of mechanical sliding parts and configured to open and close contacts; a sliding conduction part configured to electrically connect said contacts with a main circuit on receipt of a connection voltage; and a grease deposited in said mechanical sliding parts of said operating mechanism and said sliding conduction part, wherein said grease contains a base oil including at least one synthetic oil whose kinematic viscosity is 30-500 mm2/s at 40° C. and which is selected from the group consisting of poly α-olefins, poly α-olefin hydrides and dialky diphenyl ethers, and a thickener including 5-30 mass % of a urea compound. According to PTL 2, it is said that a power circuit switch can be provided in which in the operating mechanism deterioration of the grease over a period of years, deterioration of the actuation performance due to solidification, and occurrence of operating failures can be suppressed; also a power circuit switch can be provided which is of high reliability, having stable conduction performance over a long period, in which the effect of deterioration due to generation of heat on passage of current in the sliding conduction part is suppressed.